Recently, several types of communication systems coexist with the development of wireless communication techniques. Examples of the systems include a wireless communication system using a Code Division Multiple Access (CDMA) scheme referred to as a 2nd generation technique, a wireless communication system using an International Mobile Telecommunications (IMT)-2000 scheme referred to as a 3rd generation technique, and a system using an Orthogonal Frequency Division Multiple (OFDM) access scheme referred to as a 4th generation technique. In this case, the coexisting systems use different communication schemes and provide services by the use of different frequency bands. However, since limited frequency resources are used for wireless communication, there is a problem in that the frequency resources are insufficient to allow coexistence of a large number of systems.
Accordingly, there is ongoing research on a Cognitive Radio (CR) technique which uses a temporarily unused frequency band (or channel) among pre-allocated frequency bands in use. That is, even if a system is licensed for the use of a specific frequency band, the entire band is not always used. Therefore, the CR wireless communication system searches for a channel temporarily unused by the licensed system, and then provides a service through the found channel to user terminals within a service area. For example, temporarily unused frequency bands can be used among frequency bands allocated for transmission of a television (TV) signal. Herein, the licensed system is referred to as a Primary User (PU), and the CR system is referred to as a Secondary User (SU).
In order for the SU to overcome a constraint caused by the PU and to perform smooth communication, a proper resource allocation policy is required. The resource allocation policy is classified into a centralized mechanism and a distributed mechanism. The centralized mechanism is a mechanism in which a resource is allocated by a higher node such as a Base Station (BS). The distributed mechanism is a mechanism in which a resource is allocated by each user terminal. However, a special condition of the CR wireless communication system is not considered in the well-known resource allocation mechanisms. Accordingly, there is a need to propose a resource allocation method suitable for the CR wireless communication system.